Larger commercial aircraft comprise a number of different systems which according to the criticality of the functions provided by them are designed so as to be more or less redundant. Furthermore, systems are provided which in an emergency ensure, for example, the oxygen supply to passengers, or retarding or extinguishing fire in a closed-off space of the aircraft.
Providing a continuous electricity supply on board an aircraft is, for example, so elementary that very high reliability is achieved by combining several electricity supply systems. Apart from the operation of engine-driven generators, present-day aircraft comprise a ram-air-driven turbine (so called ram air turbine, RAT) for emergency use, which turbine may either provide hydraulic power and, by way of a hydraulic circuit, drive a generator, or may drive a generator directly. A ram air turbine is frequently arranged in the region of a wing-fuselage fairing, and in the case of an emergency is hinged out from a closable compartment into the airflow. During airworthiness certification flights it is often observed that turbine blades of the ram air turbine may be damaged as a result of impact by stones. Furthermore, the performance of the ram air turbine generally depends on the flight speed, and consequently in the case of approaches to land, if engine generators are unable to supply enough electrical power it may be necessary to also use a battery. In the final analysis this creates a substantial maintenance potential that clearly results in increased costs.
As an alternative, furthermore, in the context of modern commercial aircraft there are concepts relating to fuel cell systems in which exclusively from dedicated tanks oxygen and hydrogen are supplied independently of any engines. DE 10 2005 010 399 B4 shows an aircraft with a fuel cell system that is not dependent on external air, which fuel cell system comprises a fuel cell, a hydrogen tank, an oxygen tank and a power distribution unit, with fuel cell system remaining inactive during normal operation.
In order to adequately confront a fire or a fire hazard in the aircraft, commercial aircraft usually comprise a halon-based fire extinguishing system. If a fire in the cargo compartment is detected, halon is introduced into said cargo compartment, which results in suppression of the fire and prevention of the fire until the end of the flight mission. During this time the leakage from the cargo compartment needs to be picked up by the fire suppression system, in extended flight missions by flow metering bottles which ensure that whatever is lost as a result of leakage is compensated for. DE 10 2010 025 054 A1 discloses, for example, a fire extinguishing system for an aircraft, which fire extinguishing system comprises an extinguishing-agent storage device with a closure device that can be activated. Halon, for example halon 1301, is effective for extinguishing/inhibiting fires. Due to its classification as a substance that has a negative effect on the climate, and a substance that depletes the ozone layer, the production of halon 1301 is prohibited by the Montreal Protocol.
As an alternative to this, concepts exists wherein exhaust air from fuel cells is used for the inertization of a space in a transportation means, and for inhibiting minor fires. DE 10 2005 053 694 describes, for example, a fuel cell system for extinguishing fires in an aircraft, wherein the fuel cell is used to generate nitrogen-enriched air.
In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.